Integrated circuits are formed on a semiconductor substrate, which is typically composed of silicon. Such formation of integrated circuits involves sequentially forming or depositing multiple electrically conductive and insulative layers in or on the substrate. Etching processes may then be used to form geometric patterns in the layers or vias for electrical contact between the layers. Etching processes include “wet” etching, in which one or more chemical reagents are brought into direct contact with the substrate, and “dry” etching, such as plasma etching.
Various types of plasma etching processes are known in the art, including plasma etching, reactive ion (RI) etching and reactive ion beam etching. In each of these plasma processes, a gas is first introduced into a reaction chamber and then plasma is generated from the gas. This is accomplished by dissociation of the gas into ions, free radicals and electrons by using an RF (radio frequency) generator, which includes one or more electrodes. The electrodes are accelerated in an electric field generated by the electrodes, and the energized electrons strike gas molecules to form additional ions, free radicals and electrons, which strike additional gas molecules, and the plasma eventually becomes self-sustaining. The ions, free radicals and electrons in the plasma react chemically with the layer material on the semiconductor wafer to form residual products which leave the wafer surface and thus, etch the material from the wafer.
Referring to the schematic of FIG. 1, a conventional plasma etch chamber, such as a CENTURA MXP metal etch chamber available from Applied Materials, Inc., of Santa Clara, Calif., is generally indicated by reference numeral 10. The etch chamber 10 includes a housing 12 which defines a housing interior 14. A reaction chamber 18, which receives a wafer substrate (not shown) for etching, is contained in the housing interior 14. Etchant gases 17 are introduced into the housing interior 14 and the reaction chamber 18 through a gas manifold 16. During operation, volatile reaction products and unreacted etchant gases are removed from the reaction chamber 12 and the housing interior 14, as indicated by the arrows, through a throttle valve 22 mounted inside a valve housing 20 and through a gate valve 24, respectively, by operation of a turbo pump 26.
In active semiconductor fabrication process chambers, particularly those in which etching or chemical vapor deposition processes are carried out, residues frequently form on the walls and other surfaces of the chambers during processing. Accordingly, regular periodic wet chamber cleanings between wafer processing cycles is necessary for maintaining optimum system performance in the production of high-quality integrated circuit devices. Such preventative maintenance (PM) chamber cleanings require that the etch chamber lid be opened in order to facilitate physically wiping down the chamber interior.
Wet cleaning of an etch chamber 10 is shown in FIG. 2, wherein facility air down flow 28 is directed into the open etch chamber 10 during the cleaning process. When contacted by cleaning solution, some of the polymer residues which accumulate on the interior surfaces of the housing 12 and the reaction chamber 18 during the previous etching processes form residual gases 30 which diffuse or outgas from the housing 12 and reaction chamber 18 during the wet cleaning operation. For example, after an STI (shallow trench isolation) process is carried out in the etch chamber 10, such outgassing during subsequent wet cleaning includes hydrogen bromide in a time-weighted concentration average of more than 9 ppm in about 10 min. The TLV (threshold limit value) for hydrogen bromide is 3 ppm; thus, maintenance personnel who carry out the wet cleaning process must wear protective gear to minimize or prevent exposure to toxic levels of hydrogen bromide and other residual toxic gases generated during the wet cleaning process. Therefore, while personnel in the immediate vicinity of the etch chamber 10 are protected, the toxic gases tend to diffuse into the surrounding areas of the semiconductor fabrication facility where personnel without protective gear remain exposed to the gases.
According to industrial sanitation and safety standards, if potential toxic substances exist in a workplace, the first priority of health and safety personnel should be to eliminate or control the root causes or sources of such substances. The next priority is to eliminate or reduce toxin transference from the source to the personnel. The last priority is the direct protection of personnel by the use of masks, respirators or other equipment. Because no such method of direct protection is suitable for all situations and is incapable of total protection, however, the most effective prevention methods involve eliminating or controlling the root causes or sources of the toxic substances.
As shown in FIG. 3, a common method of preventing excessive outgassing of toxic gases such as hydrogen bromide during routine chamber wet cleanings involves positioning of a flow hood 32 above the etch chamber 10 and beneath the facility air down flow 28. Accordingly, most of the residual gases 30 from inside the housing 12 and reaction chamber 18 are drawn into the flow hood 32 and are evacuated from the vicinity of the etch chamber 10 through a vacuum line 34 attached to the flow hood 32. While it reduces outgassing of toxic substances, the flow hood 32 is inconvenient to use and tends to hinder access of cleaning and maintenance personnel to the interior of the etch chamber 10. Moreover, the flow hood 32 is incapable of completely preventing outgassing from the etch chamber 10, such that facility personnel remain exposed to some of the toxic fumes of the residual gas, although at reduced concentration. Accordingly, a device is needed for reducing or preventing outgassing of toxic substances such as hydrogen bromide during wet cleaning of a processing chamber.
An object of the present invention is to provide an exhaust adaptor and method for preventing or at least reducing outgassing of residual toxic gases from a process chamber during chamber cleaning or maintenance.
Another object of the present invention is to provide an exhaust adaptor and method which is capable of reducing the concentration of hydrogen bromide and other toxic gases to below occupational safety standards during cleaning or maintenance of a process chamber.
Still another object of the present invention is to provide an exhaust adaptor and method which is capable of reducing the concentration of hydrogen bromide and other toxic gases to as little as zero ppm in the vicinity around a process chamber during cleaning or maintenance of the chamber.
Yet another object of the present invention is to provide an exhaust adaptor and method which prevents injuries and health problems to facility personnel as a result of outgassing of toxic gases such as hydrogen bromide during cleaning or maintenance of a process chamber.
Another object of the present invention is to provide an exhaust adaptor and method which is capable of eliminating the need of facility personnel to wear protective gear during a chamber cleaning or maintenance process.
A still further object of the present invention is to provide an exhaust adaptor and method which facilitates unhindered access of facility personnel to the interior of a process chamber for thorough cleaning or maintenance of the chamber.
Another object of the present invention is to provide an exhaust adaptor and method which reduces or eliminates turbulent flow of air in a process chamber during chamber cleaning or maintenance.
Yet another object of the present invention is to provide an exhaust adaptor which may be connected to an exhaust bellow or conduit for the evacuation of toxic residual gases from a process chamber during cleaning or maintenance of the chamber.